1. Field of the Invention
The present invention relates to a unit for applying a friable product comprising a rigid protective shell, the product being capable of sliding in this shell between two positions, a retracted position wherein the product is protected inside the shell, and a moved-out position wherein the product can be applied to a surface to be treated.
This application unit is intended more particularly for dispensing and applying a cosmetic, dermatological or food product such as, for example, a deodorant or depilatory stick (or baton), a gel, a cream, a make-up cake, a stick of a lipstick product or cheek make-up, a blusher or a foundation cream, or a stick of glue.
2. Discussion of the Background
A lipstick case is known for example, from U.S. Pat. No. 2,491,723, wherein a product therein is able to be presented in the form of a stick. The stick is accommodated in a cup sliding inside the case. An adjusting knurled wheel provided at the bottom of the case is capable of causing the stick to advance or move back in the case. For this purpose, the knurled wheel is joined to a helix whose free end carries the cup. A device is provided for axially immobilizing a median turn of the spring, so that a rotational movement of the spring by means of the knurled wheel produces an advancing or retreating movement of the cup which holds the product. Because of the mounting of the product on the spring, this product is, as it were, suspended in an elastic manner.
The applicator of the above mentioned prior art has several drawbacks. On the one hand, the drive mechanism in accordance with U.S. Pat. No. 2,491,723 is imprecise and has play, which is detrimental to the precision of application of the product. On the other hand, at the start of the dispensing of the product, the operation of the mechanism is felt by the user as being too harsh, and at the end of the travel as too soft. Consequently, depending on the position of the cup in its shell, the softness of the application of the product is not constant. Indeed, at the start of use, when the stick is new, the softness of the application of the stick is determined by the compression of just a few turns; hence there is only a slight softness of application. On the other hand, at the end of use when the stick is almost at the end of its outward travel, the stick rests on a large number of turns of the spring and as a result the application force is too weak to obtain a proper abrasion of the product from the stick surface, which is also detrimental.